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Cancerous cooking

17 June 1995

UNREFlNED rapeseed oil used in cooking could be responsible for the high incidence of lung cancer in Chinese women, according to a new study. Past epidemiological studies have found a link between the amount of time spent cooking over woks and the risk of lung cancer.

Researchers from the Shanghai Cancer Institute and the US National Cancer Institute in Bethesda, Maryland, examined the volatile organic compounds given off by different oils at the high temperatures typically used for wok cooking.

They found that unrefined rapeseed oil produces much larger amounts of carcinogens such as benzene and formaldehyde than other cooking oils. Smoke from the oil is also much more carcinogenic than that produced by other cooking oils.

At high temperatures, the refined rapeseed oil used in the West gives off a similar amount of carcinogens as the unrefined Chinese oil. But because Western cooks do not heat their oil to such extreme temperatures, they do not produce the same haze of carcinogenic vapour.

Chinese cooks heat their oil to around 280 °C to burn off the impurities that spoil the flavour of food.